Quick connectors have been disclosed, for example, in Japanese Patent Laid-Open Publication No. 2005-282762 (Patent Document 1) and Japanese Patent Laid-Open Publication No. 2007-278508 (Patent Document 2). The quick connectors disclosed in these patent documents include a checker confirming whether a pipe body has been surely engaged with a retainer.
Operation up to when the checker confirms the engagement is as follows. When the pipe body is inserted through the retainer, an elastically-deformable claw of the retainer is expanded diametrically by an annular projection of the pipe body. Thereafter, when the annular projection of the pipe body passes through a location of the elastically-deformable claw of the retainer, the elastically-deformable claw restores its original shape, and the annular projection of the pipe body engages with the elastically-deformable claw of the retainer. On the other hand, an elastically-deformable claw of the checker is expanded diametrically by the annular projection of the pipe body that has passed through the location of the elastically-deformable claw of the retainer. The diameter expansion of the elastically-deformable claw of the checker allows the checker to become slidable. Then, by sliding the checker, it can be determined that the pipe body has been surely engaged with the retainer.